The Swedish forward was unhappy with the circumstances of his departure from Barcelona to AC Milan.
Zlatan Ibrahimovic aims to come back to haunt Barcelona
It was a late August night and, at the Camp Nou offices of Barcelona, negotiations had become tiring.
Senior executives of AC Milan sat across the table from counterparts from the reigning Spanish champions discussing how much of the €60 million (Dh 294m) Barcelona had spent signing Zlatan Ibrahimovic from Inter Milan just over a year earlier they could recoup by moving the Swede on to Inter's main rivals.
When, eventually, a deal was struck - for a year-long loan for 2010/11, then a purchase for around €25m - the player himself is said to have angrily thrown down the pen with which he signed his new contract and passed a message to the club he was leaving. "I'm going to come back and knock you out of Europe," one witness claims Ibrahimovic told Barcelona.
The undoubted tension and antipathy that developed over a season in Spain between the man who is now Serie A's leading goalscorer for the season and the head coach of Barcelona, Pep Guardiola, has had a while to dissipate.
Ibrahimovic and Guardiola now speak most respectfully about one another and Barcelona supporters appreciate that Ibrahimovic was important to winning the 2009/10 Primera Liga title.
They also know he is in ominous form. Seven Ibrahimovic goals in Milan's last four league outings have maintained the club's pole position to keep their scudetto. Domestic league titles, famously, are something Ibrahimovic collects wherever he goes.
Though Milan, Ibrahimovic, and Barcelona have met since his transfer, it was only in the group stage of the competition, earlier this season, so the chance of dealing the knockout blow he is said to have promised becomes a direct threat only over the two legs of their quarter-final meeting, which begins in San Siro tonight.
It is the most resonant of the last-eight clashes simply because of the clubs' relative status in the European Cups.
Barcelona are the dominant force of the last six years, just as Milan, under the coaches Arrigo Sacchi and Fabio Capello, were a generation ago.
In the 21st century, football looks to Barcelona for its models, its methods; at the end of the 20th, it wanted to acquire and to borrow the magic of Milan.
That partly explains the frequent traffic of individuals between the two institutions.
The modern pre-eminence of Barcelona owes much to Guardiola's predecessor, Frank Rijkaard, a Milan hero as a player and, as a coach, builder of the Barcelona side that won the 2006 Champions League.
Rijkaard had taken over a Barca low on confidence. He helped boost it by grafting on a little of his playing past. Short-term transfers of midfielders who had thrived in Italy, like the Dutchman Edgar Davids, once of Milan and Juventus, and Demetrio Albertini, an former teammate at Milan, contributed to Barcelona's rise.
The current Milan midfielder, Mark van Bommel - who serves a suspension tonight but should return for the second leg - played in the winning Barcelona team in the 2006 European Cup final against Arsenal. Xavi and Lionel Messi were not in the line-up.
That summer Rijkaard recruited the versatile full-back Gianluca Zambrotta when his then club Juventus were relegated; Zambrotta, now 35, is now with Milan.
Over the last decade, Milan have travelled on business to Barcelona in search of stardust.
Before Ibrahimovic moved from Catalonia to Lombardy, the superstars Rivaldo and Ronaldinho had done so.
It is fair to report that Barcelona had enjoyed the better years of these two Brazilians, both winners of the Ballon d'Or while they wore the Barca jersey.
In Italy, Rivaldo was a marginal figure. Ronaldinho was not. He had some memorable evenings and afternoons with Milan, though when he left just over a year ago, it was with the blessing of Massimiliano Allegri, the head coach.
Allegri would like to have Van Bommel available tonight, and indeed to name Thiago Silva, whom Barcelona covet, in the centre of his defence. The Brazilian is carrying an injury.
That, says Albertini, represents a setback for the Italian club. "An absence like that is very significant," said the former Milan and Barcelona man, who now works as vice-president of the Italian Football Federation. "Thiago Silva is excellent in one-on-ones and gives authority in the defence."
Albertini, a milanista much more than a barcelonista, says the Italians are second favourites.
"Barcelona are the best side in the world right now. Milan have experience in Europe and will be stronger than they were in the group phase, when Barcelona drew one match and won the other, but Barca have the better chance of going through."
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